Patent Grant
6853125
This application is related to Japanese patent application No. HEI 10-171179 filed on Jun. 18, 1998 whose priority is claimed under 35 USC §119, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a gas discharge display device, and more particularly to a gas discharge display device as represented by a plasma display device incorporating a PDP (Plasma Display Panel).
PDPs are becoming more and more popular as a means for television display on a large screen since their practical application to color display started. One of the problems related to image quality of PDPs is an enlargement of a reproducible color range.
2. Description of the Related Art
AC-type PDPs with a three-electrode surface-discharge structure have become commercialized as color display devices. The three-electrode AC surface-discharge PDPs have pairs of main electrodes arranged parallel to each other on individual lines (rows) of matrix display for sustaining light-emission, and address electrodes arranged one by one on individual columns. Ribs for preventing discharge interference among discharge cells are provided in a stripe pattern.
In the surface-discharge structure, fluorescent layers for color display can be provided on a substrate opposed to the substrate on which the main electrode pairs are placed, and thereby it is possible to prevent the fluorescent layers from being deteriorated by ion impact at electric discharges and to increase the life of the devices. A PDP having the fluorescent layers on a rear substrate is called a “reflection type”, and the one having the fluorescent layers on a front substrate is called a “projection type”. The reflection-type PDP is superior to the projection-type PDP in light-emission efficiency.
Usually, a Penning gas containing neon (Ne) mixed with a little amount (4 to 5%) of xenon (Xe) is used as a discharge gas. When electric discharge occurs among the main electrodes, the discharge gas emits an ultraviolet light, which in turn excites a fluorescent substance to emit light. Each pixel corresponds to three cells, and a display color is determined and set by controlling the amounts of light-emission of the fluorescent substances of three colors of R (red), G (green), and B (blue). Heretofore, compositions of the fluorescent substances and a ratio of light-emission intensities of the three colors have been selected so that a white display color may be obtained when the amount of light-emission of each of R, G, and B is given the same signal strength.
Here, a lot of research has been made on the composition of the discharge gas. Examples of known discharge gases include a three-component gas containing the above-mentioned Penning gas mixed with helium (He) or argon (Ar) (Ne+Xe+He, Ne+Xe+Ar), a two-component gas containing helium and xenon (He+Xe), and a three-component gas containing helium, argon, and xenon (He+Ar+Xe).
As described above, since the fluorescent substance is allowed to emit light by gas discharge in PDPs, a problem arises such that the color emitted from the discharge gas is mingled with the color emitted from the discharge gas.
The present invention has been made in view of these circumstances and the purpose thereof is to reduce the influence of light-emission of the discharge gas and to increase the color reproducibility.
Accordingly, the present invention provides a gas discharge display device for displaying a color image by means of first, second and third fluorescent substances having different emission colors, wherein a color to be reproduced by light-emission of the first to third fluorescent substances for displaying a white pixel is set to be different from a white color intended for display, and a filter is disposed on a front side of the first to third fluorescent substances for approximating a display color of the white pixel to the white color intended for display.
In the present invention, a filter is disposed for attenuating a light emitted by a discharge gas. Also, in order to compensate for the attenuation by the filter, the white color balance of the color reproduction by the fluorescent substances is intentionally shifted from the optimal value beforehand. For example, if a discharge gas emitting a light having a spectrum shown in
Therefore, in the present invention, the emission of light from the fluorescent substances is controlled so that the light within a wavelength region attenuated by the filter will be emitted at an intensity which is stronger by an amount attenuated by the filter. For example, if a red-cutting filter is to be provided, the amount of red light is set to be a little larger among the fluorescent substances of R, G and B. By this control, the color temperature value of the color to be reproduced by the fluorescent substances in displaying a white pixel will be lower than a color temperature value of the color (intended white color for display) which has been set as a white display color. Examples of the ways for allowing the amount of light emitted by a fluorescent substance of one color to be larger than those by the fluorescent substances of the other two colors include adoption of a material having a high luminance and increase of discharge intensity or light-emission area by changing an element structure. Element structures corresponding to the fluorescent substances of the three colors may be made different from each other to provide difference in the amount of light emission.
The present invention will be better understood from the following detailed description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings, in which:
A device according to the present invention is a gas discharge display device for displaying a color image by means of first, second and third fluorescent substances having different emission colors, wherein a color to be reproduced by light-emission of the first to third fluorescent substances for displaying a white pixel is set to be different from a white color intended for display, and a filter is disposed on a front side of the first to third fluorescent substances for approximating a display color of the white pixel to the white color intended for display.
In the gas discharge display device of the present invention, a structural condition of a display element corresponding to the first fluorescent substance may be different from structural conditions of other display elements, and a light-emission intensity of the display element corresponding to the first fluorescent substance may be higher than a light-emission intensity of the display element corresponding to the first fluorescent substance which intensity is required in reproducing a white color intended for display by means of light emission of the display elements corresponding to the first to third fluorescent substances.
In the gas discharge display device of the present invention, each of the display elements may comprise a pair of electrodes for display discharge, a fluorescent substance layer that emits light by means of electric discharge between the electrodes, and dielectric substance layers that cover the respective electrodes, and the structural condition may be an area of the electrodes.
In the gas discharge display device of the present invention, the structural condition may be an area of a light-emission region of the fluorescent substance layer.
In the gas discharge display device of the present invention, the structural condition may be a thickness of the dielectric layers.
In the gas discharge display device of the present invention, a light-emission intensity of a display element corresponding to the first fluorescent substance may be higher than a light-emission intensity of the display element corresponding to the first fluorescent substance which intensity is required in reproducing a white color intended for display by means of light-emission of the display elements corresponding to the first to third fluorescent substances.
In the gas discharge display device of the present invention, the filter may have a color correction function for increasing a color temperature value.
In the gas discharge display device of the present invention, the filter may have a characteristic of attenuating an intensity of light in a red wavelength region.
In the gas discharge display device of the present invention, the filter may have a characteristic such that an average transmissivity of light in a green wavelength region is lower than an average transmissivity of light in a blue wavelength region and higher than an average transmissivity of light in a red wavelength region.
In the gas discharge display device of the present invention, the filter may have a characteristic such that a transmissivity of a shorter wavelength side of a red wavelength region is higher than a transmissivity of a longer wavelength side of the red wavelength region.
In the gas discharge display device of the present invention, the filter may have a characteristic such that a wavelength providing the lowest transmissivity has a value within a range of 560 to 610 nanometers.
In the gas discharge display device of the present invention, the filter may have a characteristic such that absorption peaks appear at least in a wavelength region of 470 to 520 nanometers and in a wavelength region of 560 to 610 nanometers.
The gas discharge display device of the present invention may comprise a substrate that constitutes a display surface with display elements, and the filter may be formed directly on the substrate.
The gas discharge display device of the present invention may comprise a display panel incorporating a discharge space therein with arranged display elements, and the filter may be fabricated separately from the display panel and disposed on a front side of the display panel.
In the gas discharge display device of the present invention, the filter may be a pigment filter.
In the gas discharge display device of the present invention, the filter may be a multi-layer film filter.
Referring to
The PDP 1 is a three-electrode surface discharge PDP in which pairs of first and second main electrodes X and Y are disposed in parallel for generating an electric discharge for sustaining light-emission, and define cells (display elements) at intersections of the main electrodes X, Y with address electrodes A as third electrodes. The main electrodes X and Y extend in the direction of lines, i.e. in the horizontal direction, on the screen. The second main electrodes Y are used as scanning electrodes to select cells line by line in addressing. The address electrodes A extend in the direction of columns, i.e., in the vertical direction, and are used as data electrodes to select cells column by column in the addressing. A region on a substrate surface were the main electrodes intersect with the address electrodes is a display surface ES.
In the PDP-1, a pair of main electrodes X and Y is disposed on each line on an inside surface of a glass substrate 11 which is a base member for a front-side substrate assembly. The 10 line is a row of cells in the horizontal direction on the screen. The main electrodes X and Y each include an electrically conductive transparent film 41 and a metal film bus conductor) 42 and is covered with a dielectric layer 17 of a low melting point glass of about 30 μm thickness. A protection film 18 of magnesia (Mg0) of several thousand A thickness is disposed on a surface of the dielectric layer 17. The address electrodes A are arranged on an inside surface of a glass substrate 21 which is a base member for a rear-side substrate assembly 20. The address electrodes A are covered with a dielectric layer 24 of about 10 μm thickness. On the dielectric layer 24, ribs 29 of about 150 μm height are each disposed between the address electrodes A. The ribs 29 are in the form of a linear band in a plan view. These ribs 29 partition a discharge space 30 for each sub-pixel (a unit light-emission area) in the row direction and also define a gap dimension for the discharge space 30. Fluorescent layers 28R, 28G and 28B of three colors R, G, and B for color display are formed to cover a rear-side inner surface including a portion above the address electrodes A and side walls of the ribs 29. Preferable examples of the flourescent substances are shown in Table 1.
The discharge space 30 is filled with a discharge gas containing neon as a main component with which xenon (4 to 5%) is mixed. The fluorescent layers 28R, 28G, and 28B are locally excited to emit light by ultraviolet rays radiated by xenon when an electric discharge takes place. The relative ratio of the maximum luminous intensities of R, G, and B according to the present invention is set in such a manner that the luminous intensity within the attenuated wavelength region is a little stronger in order to compensate for the attenuation caused by the filter 51 or filter 52 so as to attain the best reproducibility of white color. In other words, if the filter 51 or 52 were not provided a color different from that of the original image would be reproduced. In the PDP 1 according to this embodiment, the relative ratio of the luminous intensities is set by selecting the materials to be used for the fluorescent layers 28R, 28G, and 28B.
One pixel for display is composed of three sub-pixels adjacently placed in the row direction and having different emission colors. A structural unit of each sub-pixel is a cell (a display element). Since the ribs 29 are arranged in a stripe pattern, portions of the discharge space 30 which correspond to the individual columns are continuous in the column direction, bridging all the lines. The gap of the electrodes between adjacent lines is set at a value which is sufficiently larger than the surface discharge gap (for example, a value within the range of 80 to 140 μm) and which can prevent charge coupling in the column direction (for example, a value within the range of 400 to 500 μm). An addressing discharge is generated between the main electrode Y and the address electrode A in a cell to be activated (in the case of a writing address form) or in a cell to be inactivated (in the case of an erasing address form) to form a charged state in which a suitable amount of wall charge is present only on cells to be activated for each line. Thereafter, an activation-sustaining voltage Vs is applied between the main electrodes X, Y to generate a surface discharge along the substrate surface in the cells to be activated.
In the following explanation, it is assumed that a Ne—Xe(4%) Penning gas of a composition capable of light emission having a spectrum distribution shown in
First, with reference to
The filter characteristic shown in the example of
Next, with reference to
The filter characteristic shown in the example of
Next, with reference to
The filter characteristic shown in the example of
The filter characteristic shown in the example of FIGS. BA and 8B is such that the transmissivity of visible light beams in the red wavelength region is the same as that shown in
In adopting any of the above-mentioned characteristics, it is required that the filter 51, 52 is disposed on the front side of the discharge space 30. However, there may be various choices in the form of disposing the filters. Although it is possible to dispose the filter 51, 52 on the inside of the glass substrate 11 of the PDP 1, it is preferable to dispose the filter 51, 52 on the outside of the glass substrate 11 from the view point of selection of the materials and the manufacturing steps. The filter 51, 52 may be formed either directly on the outer surface of the glass substrate 11 or on a protection plate (reinforced glass or acrylic resin plate) disposed on the front side of the glass substrate 11 through the intermediary of an air layer (gap) having a thickness of about 1.5 to 6 mm for shutting off heat generated from the PDP. If a layer having the above-mentioned characteristics is to be formed to fabricate the filter 51, 52 with a base material different from that of the glass substrate 11 or the protection plate, the base material may be a glass, an acrylic resin, a polycarbonate resin, a polymer film, or the like. From a practical point of view, the filter 51, 52 is preferably a film-like filter. For example, a desired transmissivity characteristic may be made by dispersing a suitable pigment on a surface of a polymer film and pasting the obtained film-like filter on the glass substrate 11 or the protection film. In
In the PDP 1 of the above-mentioned embodiment, the emission of light in a wavelength region which is to be attenuated by the filter is increased (intensified) by selecting a material for the fluorescent substances while maintaining the cell structures for the R, G, and B colors to be the same. In the following embodiments, the ratio of the emission intensities of the R, G, and B colors is set by allowing the cells to have different cell structures.
Next, with reference to
The PDP 2 also has a three-electrode surface-discharge structure and its basic construction is the same as that of the PDP 1. A fluorescent layer (not shown) is disposed between adjacent ribs 229 arranged in a stripe-like pattern. Three consecutive cells arranged in parallel in the direction of arranging the ribs (i.e. in the row direction) constitute one pixel. In the PDP 2, the electrically-conductive transparent film 241 and the metal film 242, which constitute the main electrodes, do not have uniform widths. Namely, the electrically conductive transparent film 241 above the R cells protrudes into the surface discharge gap and, in accordance therewith, the metal film 242 is formed to have a locally wider portion, as shown in FIG. 9. This structure allows the R cells to have a larger electrode area than the G cells or the B cells, whereby the discharge intensity of the R cells in this embodiment is increased as compared with the R cells of the prior art in which the luminance ratio of R, G, and B is set to be a value (3:6:1) for reproducing the white color of intended display. The same effect may also be obtained by allowing only the electrically conductive transparent film 241 to have a locally wider portion.
Next, with reference to
Address electrodes 3A and ribs 329 are arranged on a glass substrate 321 located on the rear side of the PDP 3, and fluorescent layers 328R, 328G, and 328B are formed between the ribs 329. In the PDP 3, the dimension D1 of the R cells in the line direction is longer than the each of the dimensions D2, D3 of the G cells and the B cells in the line direction. In other words, the emission area for the R color is larger than each of the emission areas for the G color and the B color to allow the R cells of this embodiment to generate a stronger discharge than the R cells of the prior art.
Next, with reference to
Main electrodes 412 and a dielectric layer 417 are disposed on an inner surface of a glass substrate 411 located on the front side of the PDP 4. Address electrodes 4A and ribs 429 are arranged on a glass substrate 421 located on the rear side of the PDP 4, and fluorescent layers 428R, 428G, and 428B are formed between the ribs 429. In the PDP 4, the dielectric layer 417 above the R cells has a smaller thickness than the dielectric layer 417 above the G cells or the B cells, whereby the discharge intensity of the R cells in this embodiment is increased as compared with the R cells of the prior art.
Hereto, the color temperature characteristic which has been described up to now is added. To increase the color temperature value, which is the feature of the present invention, is to set the chromaticity of white color to have coordinate values with higher color temperature on a color temperature curve chart as shown in FIG. 13.
Here, if a discharge gas other than the Ne—Xe Penning gas is to be used, the filter characteristic may be set so that the color emitted by the discharge gas is removed and the emission intensity of the light in the wavelength region which is attenuated by the filter is increased. Also, the filter for removing the color emitted by the discharge gas may be combined with individual built-in R, G, B filters that are disposed for improving the color purity in each of R, G, and B cells. Further, the emission intensity of the R color may be increased by varying the voltages supplied to the electrodes instead of varying the cell structures as mentioned above. The present invention can also be applied to a display using a gas discharge device other than the PDP.
As shown and described above, the present invention can reduce the influence of light-emission by discharge gas and increase the color reproducibility.
Although the present invention has fully been described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the invention, they should be construed as being included therein.
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